U.S. patent number 10,295,696 [Application Number 15/515,928] was granted by the patent office on 2019-05-21 for multi-component induction logging data processing in non-circular boreholes.
This patent grant is currently assigned to HALLIBURTON ENERGY SERVICES, INC.. The grantee listed for this patent is Halliburton Energy Services, Inc. Invention is credited to Junsheng Hou.
United States Patent |
10,295,696 |
Hou |
May 21, 2019 |
Multi-component induction logging data processing in non-circular
boreholes
Abstract
The processing of multicomponent induction ("MCI") data in
non-circular, or elliptical, boreholes is achieved through the use
of borehole formation models generated using elliptical borehole
characteristics.
Inventors: |
Hou; Junsheng (Kingwood,
TX) |
Applicant: |
Name |
City |
State |
Country |
Type |
Halliburton Energy Services, Inc |
Houston |
TX |
US |
|
|
Assignee: |
HALLIBURTON ENERGY SERVICES,
INC. (Houston, TX)
|
Family
ID: |
58695979 |
Appl.
No.: |
15/515,928 |
Filed: |
November 12, 2015 |
PCT
Filed: |
November 12, 2015 |
PCT No.: |
PCT/US2015/060294 |
371(c)(1),(2),(4) Date: |
March 30, 2017 |
PCT
Pub. No.: |
WO2017/082905 |
PCT
Pub. Date: |
May 18, 2017 |
Prior Publication Data
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|
|
|
Document
Identifier |
Publication Date |
|
US 20180239047 A1 |
Aug 23, 2018 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B
49/003 (20130101); G01V 3/38 (20130101); G01V
3/28 (20130101); G01V 3/30 (20130101) |
Current International
Class: |
G01V
3/10 (20060101); G01V 3/30 (20060101); E21B
49/00 (20060101); G01V 3/38 (20060101); G01V
3/28 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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WO 2011/091216 |
|
Jul 2011 |
|
WO |
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WO 2011/123379 |
|
Oct 2011 |
|
WO |
|
WO 2014/042621 |
|
Mar 2014 |
|
WO |
|
Other References
International Search Report and the Written Opinion of the
International Search Authority, or the Declaration, dated Aug. 9,
2016, PCT/US2015/060294, 17 pages, ISA/KR. cited by
applicant.
|
Primary Examiner: LaBalle; Clayton E.
Assistant Examiner: Sanghera; Jas A
Claims
What is claimed is:
1. A method for processing multi-component induction ("MCI")
logging measurement signals, the method comprising: generating a
borehole formation model based upon elliptical borehole
characteristics; acquiring a MCI measurement signal of a formation
using a logging tool extending along a borehole; processing the MCI
measurement signal using the borehole formation model; and
outputting formation property data corresponding to the processed
MCI measurement signal, wherein processing the MCI measurement
signal comprises performing an inversion of the MCI measurement
signal using the borehole formation model, and wherein performing
the inversion comprises: performing a radially one-dimensional
("R1D") inversion of the MCI measurement signal using the borehole
formation model; and removing borehole effects from the MCI
measurement signal using the R1D inverted MCI measurement
signal.
2. A method as defined in claim 1, wherein generating the borehole
formation model comprises: determining the elliptical borehole
characteristics; determining circular borehole characteristics that
are equivalent to the elliptical borehole characteristics; and
utilizing the equivalent circular borehole characteristics to
generate the borehole formation model, thereby rendering the
borehole formation model a circular borehole model.
3. A method as defined in claim 1, further comprising performing a
zero dimensional ("0D") inversion of the borehole corrected MCI
measurement signal.
4. A method as defined in claim 3, further comprising: comparing
the R1D and 0D inverted MCI measurement signals; and determining
whether the borehole is circular or elliptical based on the
comparison.
5. A method as defined in claim 1, further comprising determining
whether the borehole is circular or elliptical using the borehole
formation model.
6. A method as defined in claim 1, further comprising performing a
vertically one-dimensional ("V1D") inversion of the borehole
corrected MCI measurement signal.
7. A method as defined in claim 1, wherein the formation property
data is output as one or more of a formation horizontal
resistivity, formation vertical resistivity, dip, or azimuth.
8. A method as defined in claim 1, wherein the logging tool forms
part of a logging while drilling or wireline assembly.
9. A multi-component induction ("MCI") logging tool, comprising one
or more sensors to acquire multi-component induction measurement
signals, the sensors being communicably coupled to processing
circuitry to implement a method comprising: generating a borehole
formation model based upon elliptical borehole characteristics;
acquiring an MCI measurement signal of a formation; processing the
MCI measurement signal using the borehole formation model; and
outputting formation property data corresponding to the processed
MCI measurement signal, wherein processing the MCI measurement
signal comprises performing an inversion of the MCI measurement
signal using the borehole formation model, and wherein performing
the inversion comprises: performing a radially one-dimensional
("R1D") inversion of the MCI measurement signal using the borehole
formation model; and removing borehole effects from the MCI
measurement signal using the R1D inverted MCI measurement
signal.
10. A logging tool as defined in claim 9, wherein generating the
borehole formation model comprises: determining the elliptical
borehole characteristics; determining circular borehole
characteristics that are equivalent to the elliptical borehole
characteristics; and utilizing the equivalent circular borehole
characteristics to generate the borehole formation model, thereby
rendering the borehole formation model a circular borehole
model.
11. A logging tool as defined in claim 9, further comprising
performing a zero dimensional ("0D") inversion of the borehole
corrected MCI measurement signal.
12. A logging tool as defined in claim 11, further comprising:
comparing the R1D and 0D inverted MCI measurement signals; and
determining whether the borehole is circular or elliptical based on
the comparison.
13. A logging tool as defined in claim 9, further comprising
determining whether the borehole is circular or elliptical using
the borehole formation model.
14. A logging tool as defined in claim 9, further comprising
performing a vertically one-dimensional ("V1D") inversion of the
borehole corrected MCI measurement signal.
15. A logging tool as defined in claim 9, wherein the formation
property data is output as one or more of a formation horizontal
resistivity, formation vertical resistivity, dip, or azimuth.
16. A logging tool as defined in claim 9, wherein the logging tool
forms part of a logging while drilling or wireline assembly.
17. A logging tool as defined in claim 9, wherein the logging tool
forms part of a wireline or drilling assembly.
18. A non-transitory computer-readable medium comprising
instructions which, when executed by at least one processor, causes
the processor to perform a method comprising: generating a borehole
formation model based upon elliptical borehole characteristics;
acquiring a multi-component induction ("MCI") measurement signal of
a formation using a logging tool extending along a borehole;
processing the MCI measurement signal using the borehole formation
model, wherein processing the MCI measurement signal comprises
performing an inversion of the MCI measurement signal using the
borehole formation model, wherein performing the inversion
comprises: performing a radially one-dimensional ("R1D") inversion
of the MCI measurement signal using the circular borehole model;
and removing borehole effects from the MCI measurement signal using
the R1D inverted MCI measurement signal; and outputting formation
property data corresponding to the processed MCI measurement
signal.
19. A computer-readable medium as defined in claim 18, wherein
generating the borehole formation model comprises: deter-mining the
elliptical borehole characteristics; determining circular borehole
characteristics that are equivalent to the elliptical borehole
characteristics; and utilizing the equivalent circular borehole
characteristics to generate the borehole formation model, thereby
rendering the borehole formation model a circular borehole
model.
20. A computer-readable medium as defined in claim 18, further
comprising performing a zero dimensional ("0D") inversion of the
borehole corrected MCI measurement signal.
21. A computer-readable medium as defined in claim 20, further
comprising: comparing the R1D and 0D inverted MCI measurement
signals; and determining whether the borehole is circular or
elliptical based on the comparison.
22. A computer-readable medium as defined in claim 18, further
comprising determining whether the borehole is circular or
elliptical using the borehole formation model.
23. A computer-readable medium as defined in claim 18, further
comprising performing a vertically one-dimensional ("V1D")
inversion of the borehole corrected MCI measurement signal.
24. A computer-readable medium as defined in claim 18, wherein the
formation property data is output as one or more of a formation
horizontal resistivity, formation vertical resistivity, dip, or
azimuth.
25. A method for processing multi-component induction ("MCI")
logging measurement signals, the method comprising: generating a
borehole formation model based upon elliptical borehole
characteristics, wherein generating the borehole formation model
comprises: determining the elliptical borehole characteristics;
determining circular borehole characteristics that are equivalent
to the elliptical borehole characteristics; and utilizing the
equivalent circular borehole characteristics to generate the
borehole formation model, thereby rendering the borehole formation
model a circular borehole model; acquiring a MCI measurement signal
of a formation using a logging tool extending along a borehole;
processing the MCI measurement signal using the borehole formation
model, wherein processing the MCI measurement signal comprises:
performing a radially one-dimensional ("R1D") inversion of the MCI
measurement signal using the circular borehole model; performing a
R1D inversion of the MCI measurement signal using an elliptical
borehole model; and removing borehole effects from the MCI
measurement signal using the R1D inverted measurement signal of the
elliptical borehole model; and outputting formation property data
corresponding to the processed MCI measurement signal.
26. A method as defined in claim 25, further comprising determining
whether the borehole is circular or elliptical using the borehole
formation model.
27. A method as defined in claim 25, wherein the formation property
data is output as one or more of a formation horizontal
resistivity, formation vertical resistivity, dip, or azimuth.
28. A method as defined in claim 25, further comprising: comparing
the R1D inverted MCI measurement signal of the circular borehole
model to the R1D inverted MCI measurement signal of the elliptical
borehole model; and determining whether the borehole is circular or
elliptical based on the comparison.
29. A method as defined in claim 25, further comprising performing
a vertically one-dimensional ("V1D") inversion of the borehole
corrected MCI measurement signal.
30. A method as defined in claim 25, wherein the logging tool forms
part of a logging while drilling or wireline assembly.
31. A multi-component induction ("MCI") logging tool, comprising
one or more sensors to acquire multi-component induction
measurement signals, the sensors being communicably coupled to
processing circuitry to implement a method comprising: generating a
borehole formation model based upon elliptical borehole
characteristics, wherein generating the borehole formation model
comprises: determining the elliptical borehole characteristics;
determining circular borehole characteristics that are equivalent
to the elliptical borehole characteristics; and utilizing the
equivalent circular borehole characteristics to generate the
borehole formation model, thereby rendering the borehole formation
model a circular borehole model; acquiring an MCI measurement
signal of a formation; processing the MCI measurement signal using
the borehole formation model, wherein the processing comprises:
performing a radially one-dimensional ("R1D") inversion of the MCI
measurement signal using the circular borehole model; performing a
R1D inversion of the MCI measurement signal using an elliptical
borehole model; and removing borehole effects from the MCI
measurement signal using the R1D inverted measurement signal of the
elliptical borehole model; and outputting formation property data
corresponding to the processed MCI measurement signal.
32. A logging tool as defined in claim 31, further comprising
determining whether the borehole is circular or elliptical using
the borehole formation model.
33. A logging tool as defined in claim 31, wherein the formation
property data is output as one or more of a formation horizontal
resistivity, formation vertical resistivity, dip, or azimuth.
34. A logging tool as defined in claim 31, further comprising:
comparing the R1D inverted MCI measurement signal of the circular
borehole model to the R1D inverted MCI measurement signal of the
elliptical borehole model; and determining whether the borehole is
circular or elliptical based on the comparison.
35. A logging tool as defined in claim 31, further comprising
performing a vertically one-dimensional ("V1D") inversion of the
borehole corrected MCI measurement signal.
36. A logging tool as defined in claim 31, wherein the logging tool
forms part of a logging while drilling or wireline assembly.
37. A logging tool as defined in claim 31, wherein the logging tool
forms part of a wireline or drilling assembly.
38. A non-transitory computer-readable medium comprising
instructions which, when executed by at least one processor, causes
the processor to perform a method comprising: generating a borehole
formation model based upon elliptical borehole characteristics,
wherein generating the borehole formation model comprises:
determining the elliptical borehole characteristics; determining
circular borehole characteristics that are equivalent to the
elliptical borehole characteristics; and utilizing the equivalent
circular borehole characteristics to generate the borehole
formation model, thereby rendering the borehole formation model a
circular borehole model; acquiring a multi-component induction
("MCI") measurement signal of a formation using a logging tool
extending along a borehole; processing the MCI measurement signal
using the borehole formation model, wherein processing the MCI
measurement signal comprises: performing a radially one-dimensional
("R1D") inversion of the MCI measurement signal using the circular
borehole model; performing a R1D inversion of the MCI measurement
signal using an elliptical borehole model; and removing borehole
effects from the MCI measurement signal using the R1D inverted
measurement signal of the elliptical borehole model; and outputting
formation property data corresponding to the processed MCI
measurement signal.
39. A non-transitory computer-readable medium as defined in claim
38, further comprising determining whether the borehole is circular
or elliptical using the borehole formation model.
40. A non-transitory computer-readable medium as defined in claim
38, wherein the formation property data is output as one or more of
a formation horizontal resistivity, formation vertical resistivity,
dip, or azimuth.
41. A non-transitory computer-readable medium as defined in claim
38, further comprising: comparing the R1D inverted MCI measurement
signal of the circular borehole model to the R1D inverted MCI
measurement signal of the elliptical borehole model; and
determining whether the borehole is circular or elliptical based on
the comparison.
42. A non-transitory computer-readable medium as defined in claim
38, further comprising performing a vertically one-dimensional
("V1D") inversion of the borehole corrected MCI measurement signal.
Description
PRIORITY
The present application is a U.S. National Stage patent application
of International Patent Application No. PCT/US2015/060294, filed on
Nov. 12, 2015, the benefit of which is claimed and the disclosure
of which is incorporated herein by reference in its entirety.
FIELD OF THE DISCLOSURE
The present disclosure relates generally to downhole logging and,
more specifically, to processing multi-component induction ("MCI")
logging measurements in non-circular boreholes.
BACKGROUND
Downhole logging tools are utilized to acquire various
characteristics of earth formations traversed by the borehole, as
well as data relating to the size and shape of the borehole itself.
The collection of information relating to downhole conditions,
commonly referred to as "logging," can be performed by several
methods including wireline logging, "logging while drilling"
("LWD") and "measuring while drilling ("MWD").
Many boreholes have a non-circular (or oval) shape after drilling,
especially in deviated and horizontal wells. As a result of the
tectonic forces, the oval shape is created due to the effect of
pressures in the crust being different in different directions.
Currently, multi-component induction data processing methods based
on circular-hole models are available for the well logging
industry. As a result, when the borehole has a non-circular shape,
the acquired formation properties (e.g., resistivity and dip) are
inaccurate because they are based on circular borehole models.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a 3D side view and a top-down 2D view of a
circular borehole formation model used for MCI data processing,
according to certain illustrative methods of the present
disclosure;
FIG. 2 provides a flow chart of a method for data processing of MCI
measurement signals using a circular borehole model, according to
certain illustrative methods of the present disclosure;
FIG. 3 illustrates a method for processing the MCI measurement
signals using a circular borehole model, according to certain
illustrative methods of the present disclosure;
FIG. 4 illustrates a 3D side view and a top-down 2D view of an
elliptical borehole formation model used for MCI data processing,
according to certain alternative illustrative methods of the
present disclosure;
FIG. 5 illustrates a method for processing the MCI measurement
signals using an elliptical borehole model, according to certain
illustrative methods of the present disclosure;
FIG. 6A illustrates an MCI logging tool, utilized in an LWD
application, that acquires MCI measurement signals processed using
the illustrative methods described herein; and
FIG. 6B illustrates an alternative embodiment of the present
disclosure whereby a wireline MCI logging tool acquires and
processes the MCI measurement signals.
DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
Illustrative embodiments and related methodologies of the present
disclosure are described below as they might be employed in methods
and systems to process MCI data acquired in non-circular boreholes.
In the interest of clarity, not all features of an actual
implementation or methodology are described in this specification.
It will of course be appreciated that in the development of any
such actual embodiment, numerous implementation-specific decisions
must be made to achieve the developers' specific goals, such as
compliance with system-related and business-related constraints,
which will vary from one implementation to another. Moreover, it
will be appreciated that such a development effort might be complex
and time-consuming, but would nevertheless be a routine undertaking
for those of ordinary skill in the art having the benefit of this
disclosure. Further aspects and advantages of the various
embodiments and related methodologies of the disclosure will become
apparent from consideration of the following description and
drawings.
As described herein, illustrative systems and methods of the
present disclosure are directed to processing MCI measurement data
acquired in non-circular boreholes. In a generalized method, an MCI
logging tool is deployed downhole along a non-circular borehole,
and MCI measurement signals are acquired. A borehole formation
model is generated using characteristics of the non-circular
borehole, and the acquired MCI measurement signals are processed
using the borehole formation model. Formation property data
corresponding to the processed MCI measurement signals are then
output.
The generalized method may be implemented in two ways. In a first
method, electromagnetic and geometric equivalence is utilized to
generate the borehole formation model. In this method, the
non-circular (or elliptical) borehole characteristics of the
borehole are determined. Circular borehole characteristics
equivalent to the elliptical borehole characteristics are then
determined. The equivalent borehole characteristics are utilized to
generate the borehole formation model, thereby creating a circular
borehole model. The borehole effects of the MCI measurement signal
is then removed using a radially one-dimensional ("R1D") inversion
based on the circular borehole model, resulting in highly accurate
processing of the formation property data.
In the second method, the MCI data processing is accomplished using
a borehole formation model based on an elliptical borehole with a
full space (zero-dimensional or "0D") formation. In this method, an
R1D inversion of the MCI measurement signal is conducted using the
circular borehole formation model mentioned above. Another R1D
inversion of the MCI measurement signal is then performed using an
elliptical borehole model. Thereafter, the borehole effects of the
MCI measurement signal are removed using the R1D inversion of the
elliptical borehole model, thereby resulting in highly accurate
formation property data.
Therefore, as described herein, a novel data processing method of
MCI measurements in non-circular boreholes is provided through the
use of a circular borehole model or a non-circular (or oval)
borehole model. Once the methods are performed, the processed
formation anisotropy (horizontal and vertical resistitivities), dip
(and azimuth), and corrected induction logs, as well as the oval
identification index ("OII") can be obtained. These and other
advantages of the present disclosure will be apparent to those
ordinarily skilled in the art having the benefit of this
disclosure.
As will be noted throughout this disclosure, the real borehole
cross section can be circular or non-circular (or oval). For the
non-circular or oval shape, it is geometrically a plane curve named
after Rene Descartes, the set of points that have the same linear
combination of distances from two fixed points in a Cartesian
system. As such, their shape does not depart much from that of an
ellipse. Therefore, in the following description, a borehole having
an oval shape is assumed and mathematically described as an
ellipse.
As will be understood by those ordinarily skilled in the art having
the benefit of this disclosure, a circle is defined as a closed
curved shape that is flat. That is, it exists in two dimensions or
on a plane. In a circle, all points on the circle are equally far
from the center of the circle. In contrast, an ellipse is also a
closed curved shape that is flat. However, all points on the
ellipse are not the same distance from the center point of the
ellipse.
FIG. 1 illustrates a 3D side view and a top-down 2D view of a
circular borehole formation model used for MCI data processing,
according to certain illustrative methods of the present
disclosure. The circular borehole formation model consists of a
circular-shaped hole surrounded by a full-space (or 0D)
transversely isotropic ("TI") formation, which is used for R1D
inversion and MCI borehole correction. The left panel is its 3D
view and the right panel is its top 2D view in the x.sub.t-y.sub.t
plane. In this example, (x.sub.t, y.sub.t, z.sub.t) is the
tool/measurement coordinate system, (x.sub.f, y.sub.f, z.sub.f) is
the formation coordinate system, and (x.sub.s, y.sub.s,
z.sub.s=z.sub.t) is the strike coordinate system.
The borehole shape is described by a parameter of the circle radius
or diameter, frequently denoted by r. In FIG. 1, this model usually
consists of a borehole with a circular cross section surrounded by
an infinitely thick homogeneous formation. The borehole may be
vertical or deviated, and the MCI logging tool can be centralized
or decentralized in the borehole. An illustrative MCI logging tool
is the Xaminer.TM.-MCI logging tool, which is commercially
available through Halliburton Energy Services, Inc. of Houston,
Tex. Formation resistivity/conductivity can be isotropic or
anisotropic. Numerical simulations show that for a given subarray
operated at a given frequency, the MCI apparent conductivity tensor
.sigma..sub.a with nine components depends on the following nine
borehole-formation parameters:
Rh=the formation horizontal resistivity (or horizontal
conductivity) in ohm-m.
Rv=the formation vertical resistivity (or vertical conductivity) in
ohm-m.
Rvh=the anisotropic ratio (Rvh=Rv/Rh).
.PHI.=the formation/borehole strike or azimuth, in degrees.
r=the borehole radius, in inches or meters.
R.sub.m=the borehole mud resistivity, in ohm-m.
d.sub.e=the MCI logging tool's eccentric distance, given by the
distance from the borehole center to the center of the tool, or as
an eccentricity ratio (ecc=d.sub.e/r).
.phi..sub.e=the MCI logging tool eccentricity azimuthal angle in
the tool/measurement coordinate system. Moreover, .phi..sub.e.sup.s
is the tool eccentricity angle in the strike system
.phi..sub.e.sup.s=.phi.e-.PHI..sub.s, in degrees.
dip=the relative dip angle between the formation and borehole, in
degrees.
Based on the circular borehole model of FIG. 1, an MCI response
library (i.e., modeled tool responses) can be pre-calculated
(before real measurement data is acquired by the logging tool) by
using a numerical simulation algorithm such as, for example, the
three-dimensional finite difference ("3DFD") method or
three-dimensional finite element ("3DFE"). Once the MCI response
library is pre-populated, it is then also used as the forward
engine in processing the subsequent MCI measurement data acquired
during logging operations.
In certain methods of the present disclosure, the MCI logging tool
is combined with a multi-arm caliper tool (e.g., Halliburton Energy
Services, Inc.'s LOGIQ.RTM. Caliper Tool), which is used for
determining the borehole shape (i.e., circular or elliptical
borehole characteristics) and tool position inside the borehole
(e.g., tool eccentricity and its azimuthal angle). In those cases
where the borehole is elliptically shaped, once the borehole shape
and tool position are determined, the equivalent circular radius
(i.e., equivalent circular borehole characteristics) can be
pre-calculated by the following equations: .pi.r.sup.2=.pi.ab (1a),
and r= ab (1b), or .pi.r.sup.2=1/2.pi.(a.sup.2+b.sup.2) (2a), and
r= (1/2(a.sup.2+b.sup.2)) (2b).
Here, in Equations (1a) and (1b), a is the half length of the major
axis and b is the half length of the minor axis of an ellipse,
which are evaluated from the multi-arm caliper measurements. In
other words, an ellipse is replaced by an equivalent circle with a
radius denoted by r, which is the geometric mean of a and b.
Alternatively, the radius r is calculated by Equations (2a) and
(2b) where the radius r is the root-mean-square (RMS) average of a
and b. Finally, the following arithmetic average equation (3) may
then be used to determine the radius of the equivalent circle:
r=1/2(a+b) (3). Thus, the equivalent circular borehole
characteristics are utilized to generate the circular borehole
model.
In view of this geometric area and electromagnetic field
equivalence described above, FIG. 2 provides a flow chart of a
method 200 for data processing of MCI measurement signals using a
circular borehole model, according to certain illustrative methods
of the present disclosure. At block 202, a borehole formation model
is generated based upon elliptical borehole characteristics as
described above in relation to FIG. 1. The borehole characteristics
may be, for example, the borehole shape and tool position inside
the borehole (e.g., tool eccentricity or azimuthal angle). These
elliptical borehole characteristics may be acquired from the actual
borehole in which the MCI logging tool is deployed (e.g., acquired
using a caliper tool), other similar boreholes, or borehole
models.
As will be described in more detail below, the borehole formation
model may be generated in one of two ways. In a first method, the
elliptical borehole characteristics may be converted into
equivalent circular borehole characteristics, which are then used
to generate a circular borehole model. Alternatively, the
elliptical borehole characteristics are used to generate an
elliptical borehole model, which will also be described in more
detail below.
At block 204, after the MCI logging tool has been deployed downhole
into the borehole, one or more MCI measurement signal(s) of the
formation are acquired using the MCI logging tool. At block 206,
the MCI measurement signal(s) are then processed using the borehole
formation model. At block 208, formation property data which
corresponds to the processed MCI measurement signal(s) are then
output as desired.
FIG. 3 illustrates a method 300 for processing the MCI measurement
signals using a circular borehole model, according to certain
illustrative methods of the present disclosure. At block 302, the
MCI library and process control information is input into the
logging system database. As previously described, the MCI response
library may be generated using data pre-calculated by numerical
simulation algorithms performed on the circular borehole model of
FIG. 1. This same circular borehole model will be used later as the
forward engine to process the acquired MCI measurement signals. The
process control information input here may be, for example, the
sample rate of the logging tool, mud type, or logging
direction.
After the MCI logging tool is deployed downhole and MCI measurement
signal(s) are acquired, the MCI measurement signal data is
calibrated and temperature corrected, and then input into the
circular borehole model at block 304. Calibration and temperature
correction is necessary because the raw measured data are induction
voltages which are affected by downhole temperatures. At block 306,
a radially one-dimensional ("R1D") inversion of the MCI measurement
signal(s) is performed using the circular borehole model.
In the R1D inversion of block 306, the inverted formation
horizontal and vertical resistivities (Rh and Rv) and dip are not
the true formation parameters if the cross section of the borehole
is elliptical in nature. In such cases, Rh, Rv and dip are only
equivalents of the true formation parameters. However, these
equivalent formation parameters are then utilized in block 308 for
borehole correction based on the circular borehole model. Once
borehole correction is complete, a zero-dimensional ("0D")
inversion of the borehole corrected MCI measurement signal data is
performed at block 310, thereby resulting in the true formation Rh,
Rv, dip, and/or azimuth/strike. Here, the 0D inversion is based on
a full-space homogeneous formation model.
In certain illustrative methods, oval identification of the
borehole may be performed at block 312. Here, the R1D and 0D
inverted MCI measurement signal data is compared to determine if
the borehole shape is circular or elliptical by computing the
following oval identification index ("OII"):
OII=w.sub.Rh.DELTA..sub.Rh+w.sub.Rv.DELTA..sub.Rv+w.sub.dip.DELTA..sub.di-
p (4).
Here, w.sub.Rh,w.sub.RV and w.sub.dip are the weighted coefficients
for formation Rh, Rv, and dip and w.sub.Rh+w.sub.Ry+w.sub.dip=1.
The weighted coefficients are a function of tool spacing,
frequencies, Rh, Rv, and dip sensitivity to the hole shape.
.DELTA..sub.Rh, .DELTA..sub.Rv, and .DELTA..sub.dip are determined
by using the following three equations:
.DELTA..times..times..times..times..times..times..times..times..times..ti-
mes..times..DELTA..times..times..times..times..times..times..times..times.-
.times..times..times..DELTA..times..times..times..times..times..times..tim-
es..times..times..times..times..times..DELTA..times..times..times..times..-
times..times..times..times..times..times..times. ##EQU00001##
In Equations (5a), (5b), and (5c) above, Rh.sup.(R1D),
Rv.sup.(R1D), and dip.sup.(R1D) are the inverted results of the
three formation parameters from the R1D inversion at block 306, and
Rh.sup.(0D), Rv.sup.(0D), and dip.sup.(0D) are the inverted results
from the 0D inversion at block 310. From those 3 equations, it can
be seen how the OII is very close to zero if the borehole is
circular while ignoring the shoulder bed effects. Accordingly, the
above equations are utilized to identify if the borehole is
circular or ellipse at block 312.
Since the 0D inversion ignores the layer effect of the formation as
it pertains to the resistivity data, certain illustrative methods
of the present disclosure also perform a vertically one-dimensional
("V1D") inversion of the borehole corrected MCI measurement
signal(s) at block 314. Here, the V1D inversion takes into account
the layer effects of the formation. The final processed
data/results are output at block 316.
Accordingly, the illustrative processing method described above not
only delivers the formation Rh, Rv, dip, and azimuth in real-time,
but also provides the borehole shape information. Once the borehole
shape is known, this data may be used for subsequent geological
stress analysis.
FIG. 4 illustrates a 3D side view and a top-down 2D view of an
elliptical borehole formation model used for MCI data processing,
according to certain alternative illustrative methods of the
present disclosure. An elliptical borehole model used for the MCI
data processing is shown in FIG. 4, in which the borehole shape is
described by a parameter of the circle radius or diameter,
frequently denoted by r. The elliptical borehole model consists of
an ellipse-shaped borehole surrounded by a full-space (or 0D) TI
formation used for R1D inversion and MCI borehole correction. All
others variables are the same as those of FIG. 1. The primary
difference is the ellipse-shaped hole replaces the circular hole,
which leads to the hole shape being described by two basic
parameters of the major axis a and the minor axis b of an ellipse.
FIG. 4 shows the elliptical model as being described by the
following parameters: Rh, Rv (or Rvh), .PHI..sub.s, borehole major
and minor radius a and b, R.sub.m, d.sub.e (or ecc=2d.sub.e/(a+b)),
and .phi..sub.e or (.phi..sub.e-.PHI..sub.s). Based on this model,
the MCI response library is again pre-built by using the fast and
accurate electromagnetic algorithms, such as, for example, 3DFD or
3DFE numerical methods previously described. As such, the MCI
response library includes the modeled tool responses of both the
circular and elliptical borehole models. In the same way, the
elliptical borehole model is also used as the forward engine in the
MCI data processing.
FIG. 5 illustrates a method 500 for processing the MCI measurement
signals using an elliptical borehole model, according to certain
illustrative methods of the present disclosure. When comparing
method 300 to method 500, it can be seen that the workflows have
some similarities, but there are also some differences. At block
502, the MCI library and process control information are again
input into the logging system database. After the MCI measurements
are acquired, they are calibrated and temperature corrected at
block 504, also previously described.
In order to determine the initial borehole diameter, Equations
(1a)-(3) are utilized. Here, two MCI libraries are necessary: one
based on the circular borehole model, and the other based on the
elliptical borehole model. At block 506, a R1D inversion of the MCI
measurement signal(s) is performed using the circular borehole
model. This R1D inversion based on the circle model provides the
initial estimate for all inverted parameters. At block 508, a R1D
inversion of the MCI measurement signal(s) is performed using the
elliptical borehole model. At block 510, the borehole effects are
removed from the MCI measurement signal(s) using the R1D inverted
measurement signal(s) of the elliptical borehole model, whereby the
borehole correction of block 510 provides the final output of Rh,
Rv, Dip, and so on.
Thereafter, in alternative methods, the shape of the borehole may
be determined at block 512. Here, the two R1D inversions of the
circular and elliptical borehole models are compared to compute the
oval identification. In block 512, the following equations are
utilized:
.DELTA..times..times..times..DELTA..times..times..times..times..DELTA..ti-
mes..times..times. ##EQU00002##
In equations (6a), (6b), and (6c) above, Rh.sup.(ell),
Rv.sup.(ell), and dip.sup.(ell) are the inverted results of the
three formation parameters from the R1D inversion based on the
elliptical borehole model, and Rh.sup.(cir), Rv.sup.(cir), and
dip.sup.(cir) are the inverted results from the R1D inversion based
on the circular borehole model. At block 514, a V1D inversion of
the borehole corrected MCI measurement signal(s) is performed in
order to determine the formation property values of Rh, Rv, dip and
azimuth. Thereafter, all processed log data are output for other
applications, such as, for example, the calculation of sand Rt
(which is the sandstone resistivity) and oil/gas saturation.
Now that a variety of alternative workflows of the present
disclosure have been described, illustrative applications will now
be described. FIG. 6A illustrates an MCI logging tool, utilized in
an LWD application, that acquires MCI measurement signals processed
using the illustrative methods described herein. The methods
described herein may be performed by a system control center
located on the logging tool or may be conducted by a processing
unit at a remote location, such as, for example, the surface.
FIG. 6A illustrates a drilling platform 602 equipped with a derrick
604 that supports a hoist 606 for raising and lowering a drill
string 608. Hoist 606 suspends a top drive 610 suitable for
rotating drill string 608 and lowering it through well head 612.
Connected to the lower end of drill string 608 is a drill bit 614.
As drill bit 614 rotates, it creates a wellbore 616 that passes
through various layers of a formation 618. A pump 620 circulates
drilling fluid through a supply pipe 622 to top drive 610, down
through the interior of drill string 608, through orifices in drill
bit 614, back to the surface via the annulus around drill string
608, and into a retention pit 624. The drilling fluid transports
cuttings from the borehole into pit 24 and aids in maintaining the
integrity of wellbore 616. Various materials can be used for
drilling fluid, including, but not limited to, a salt-water based
conductive mud.
An MCI logging tool 626 is integrated into the bottom-hole assembly
near the bit 614. In this illustrative embodiment, MCI logging tool
626 is an LWD tool; however, in other illustrative embodiments, MCI
logging tool 626 may be utilized in a wireline or tubing-conveyed
logging application. In certain illustrative embodiments, MCI
logging tool 626 may be adapted to perform logging operations in
both open and cased hole environments.
As drill bit 614 extends wellbore 616 through formations 618, MCI
logging tool 626 collects measurement signals relating to various
formation properties, as well as the tool orientation and various
other drilling conditions. In certain embodiments, MCI logging tool
626 may take the form of a drill collar, i.e., a thick-walled
tubular that provides weight and rigidity to aid the drilling
process. However, as described herein, logging tool 626 includes an
induction or propagation resistivity tool to sense geology and
resistivity of formations. A telemetry sub 628 may be included to
transfer images and measurement data/signals to a surface receiver
630 and to receive commands from the surface. In some embodiments,
telemetry sub 628 does not communicate with the surface, but rather
stores logging data for later retrieval at the surface when the
logging assembly is recovered.
Still referring to FIG. 6A, MCI logging tool 626 includes a system
control center ("SCC"), along with necessary
processing/storage/communication circuitry, that is communicably
coupled to one or more sensors (not shown) utilized to acquire
formation measurement signals reflecting formation parameters. In
certain embodiments, once the measurement signals are acquired, the
system control center calibrates the measurement signals, performs
the processing methods describes herein, and then communicates the
data back uphole and/or to other assembly components via telemetry
sub 628. In an alternate embodiment, the system control center may
be located at a remote location away from MCI logging tool 626,
such as the surface or in a different borehole, and performs the
processing accordingly. These and other variations within the
present disclosure will be readily apparent to those ordinarily
skilled in the art having the benefit of this disclosure.
The logging sensors utilized along logging tool 626 are resistivity
sensors, such as, for example, magnetic or electric sensors, and
may communicate in real-time. Illustrative magnetic sensors may
include coil windings and solenoid windings that utilize induction
phenomenon to sense conductivity of the earth formations.
Illustrative electric sensors may include electrodes, linear wire
antennas or toroidal antennas that utilize Ohm's law to perform the
measurement. In addition, the sensors may be realizations of
dipoles with an azimuthal moment direction and directionality, such
as tilted coil antennas. In addition, the logging sensors may be
adapted to perform logging operations in the up-hole or downhole
directions. Telemetry sub 628 communicates with a remote location
(surface, for example) using, for example, acoustic, pressure
pulse, or electromagnetic methodologies, as will be understood by
those ordinarily skilled in the art having the benefit of this
disclosure.
MCI logging tool 626 may be, for example, a deep sensing induction
or propagation resistivity tool. As will be understood by those
ordinarily skilled in the art having the benefit of this
disclosure, such tools typically include one or more transmitter
and receiver coils that are axially separated along the wellbore
616. The transmitter coils generate alternating displacement
currents in the formation 618 that are a function of conductivity.
The alternating currents generate voltage at the one or more
receiver coils. In addition to the path through the formation 618,
a direct path from the transmitter coil(s) to receiver coil(s) also
exists. In induction tools, signal from such path can be eliminated
by the use of an oppositely wound and axially offset "bucking"
coil. In propagation tools, phase and amplitude of the
complex-valued voltage can be measured at certain operating
frequencies. In such tools, it is also possible to measure phase
difference and amplitude ratio between of the complex-valued
voltages at two axially spaced receivers. Furthermore,
pulse-excitation excitation and time-domain measurement signals can
be used in the place of frequency domain measurement signals. Such
measurement signals can be transformed into frequency measurements
by utilizing a Fourier transform. The calibration methods described
below are applicable to all of these signals and no limitation is
intended with the presented examples. Generally speaking, a greater
depth of investigation can be achieved using a larger
transmitter-receiver pair spacing, but the vertical resolution of
the measurement signals may suffer. Accordingly, logging tool 626
may employ multiple sets of transmitters or receivers at different
positions along the wellbore 616 to enable multiple depths of
investigation without unduly sacrificing vertical resolution.
FIG. 6B illustrates an alternative embodiment of the present
disclosure whereby a wireline MCI logging tool acquires and
processes the MCI measurement signals. At various times during the
drilling process, drill string 608 may be removed from the borehole
as shown in FIG. 6B. Once drill string 608 has been removed,
logging operations can be conducted using a wireline MCI logging
sonde 634, i.e., a probe suspended by a cable 641 having conductors
for transporting power to the sonde and telemetry from the sonde to
the surface. A wireline MCI logging sonde 634 may have pads and/or
centralizing springs to maintain the tool near the axis of the
borehole as the tool is pulled uphole. MCI Logging sonde 634 can
include a variety of sensors including a multi-array laterolog tool
for measuring formation resistivity. A logging facility 643
collects measurements from the MCI logging sonde 634, and includes
a computer system 645 for processing and storing the measurements
gathered by the sensors, as described herein.
In certain illustrative embodiments, the system control centers
utilized by the MCI logging tools described herein include at least
one processor embodied within system control center and a
non-transitory and computer-readable medium, all interconnected via
a system bus. Software instructions executable by the processor for
implementing the illustrative MCI data processing methods described
herein in may be stored in local storage or some other
computer-readable medium. It will also be recognized that the MCI
processing software instructions may also be loaded into the
storage from a CD-ROM or other appropriate storage media via wired
or wireless methods.
Moreover, those ordinarily skilled in the art will appreciate that
various aspects of the disclosure may be practiced with a variety
of computer-system configurations, including hand-held devices,
multiprocessor systems, microprocessor-based or
programmable-consumer electronics, minicomputers, mainframe
computers, and the like. Any number of computer-systems and
computer networks are acceptable for use with the present
disclosure. The disclosure may be practiced in
distributed-computing environments where tasks are performed by
remote-processing devices that are linked through a communications
network. In a distributed-computing environment, program modules
may be located in both local and remote computer-storage media
including memory storage devices. The present disclosure may
therefore, be implemented in connection with various hardware,
software or a combination thereof in a computer system or other
processing system.
Accordingly, two illustrative data processing workflows for MCI
measurements based on an elliptical and circular borehole model
have been presented in this disclosure. Such methods may be used to
process MCI measurements in circular or elliptical wellbore
environments, thus resulting in more accurate data processing.
Embodiments of the present disclosure described herein further
relate to any one or more of the following paragraphs:
1. A method for processing multi-component induction ("MCI")
logging measurement signals, the method comprising generating a
borehole formation model based upon elliptical borehole
characteristics; acquiring a MCI measurement signal of a formation
using a logging tool extending along a borehole; processing the MCI
measurement signal using the borehole formation model; and
outputting formation property data corresponding to the processed
MCI measurement signal.
2. A method as defined in paragraph 1, wherein generating the
borehole formation model comprises determining the elliptical
borehole characteristics; determining circular borehole
characteristics that are equivalent to the elliptical borehole
characteristics; and utilizing the equivalent circular borehole
characteristics to generate the borehole formation model, thereby
rendering the borehole formation model a circular borehole
model.
3. A method as defined in paragraphs 1 or 2, wherein processing the
MCI measurement signal comprises performing an inversion of the MCI
measurement signal using the borehole formation model.
4. A method as defined in any of paragraphs 1-3, wherein performing
the inversion comprises performing a radially one-dimensional
("R1D") inversion of the MCI measurement signal using the circular
borehole model; and removing borehole effects from the MCI
measurement signal using the R1D inverted MCI measurement
signal.
5. A method as defined in any of paragraphs 1-4, further comprising
performing a zero dimensional ("0D") inversion of the borehole
corrected MCI measurement signal.
6. A method as defined in any of paragraphs 1-5, further comprising
comparing the R1D and 0D inverted MCI measurement signals; and
determining whether the borehole is circular or elliptical based on
the comparison.
7. A method as defined in any of paragraphs 1-6, further comprising
determining whether the borehole is circular or elliptical using
the borehole formation model.
8. A method as defined in any of paragraphs 1-7, further comprising
performing a vertically one-dimensional ("V1D") inversion of the
borehole corrected MCI measurement signal.
9. A method as defined in any of paragraphs 1-8, wherein the
formation property data is output as one or more of a formation
horizontal resistivity, formation vertical resistivity, dip, or
azimuth.
10. A method as defined in any of paragraphs 1-9, further
comprising performing a radially one-dimensional ("R1D") inversion
of the MCI measurement signal using the circular borehole model;
performing a R1D inversion of the MCI measurement signal using an
elliptical borehole model; and removing borehole effects from the
MCI measurement signal using the R1D inverted measurement signal of
the elliptical borehole model.
11. A method as defined in any of paragraphs 1-10, further
comprising comparing the R1D inverted MCI measurement signal of the
circular borehole model to the R1D inverted MCI measurement signal
of the elliptical borehole model; and determining whether the
borehole is circular or elliptical based on the comparison.
12. A method as defined in any of paragraphs 1-11, further
comprising performing a vertically one-dimensional ("V1D")
inversion of the borehole corrected MCI measurement signal.
13. A method as defined in any of paragraphs 1-12, wherein the
logging tool forms part of a logging while drilling or wireline
assembly.
14. A multi-component induction ("MCI") logging tool, comprising
one or more sensors to acquire multi-component induction
measurement signals, the sensors being communicably coupled to
processing circuitry to implement a method comprising generating a
borehole formation model based upon elliptical borehole
characteristics; acquiring an MCI measurement signal of a
formation; processing the MCI measurement signal using the borehole
formation model; and outputting formation property data
corresponding to the processed MCI measurement signal.
15. A logging tool as defined in paragraph 14, wherein generating
the borehole formation model comprises determining the elliptical
borehole characteristics; determining circular borehole
characteristics that are equivalent to the elliptical borehole
characteristics; and utilizing the equivalent circular borehole
characteristics to generate the borehole formation model, thereby
rendering the borehole formation model a circular borehole
model.
16. A logging tool as defined in paragraphs 14 or 15, wherein
processing the MCI measurement signal comprises performing an
inversion of the MCI measurement signal using the borehole
formation model.
17. A logging tool as defined in any of paragraphs 14-16, wherein
performing the inversion comprises performing a radially
one-dimensional ("R1D") inversion of the MCI measurement signal
using the circular borehole model; and removing borehole effects
from the MCI measurement signal using the R1D inverted MCI
measurement signal.
18. A logging tool as defined in any of paragraphs 14-17, further
comprising performing a zero dimensional ("0D") inversion of the
borehole corrected MCI measurement signal.
19. A logging tool as defined in any of paragraphs 14-18, further
comprising comparing the R1D and 0D inverted MCI measurement
signals; and determining whether the borehole is circular or
elliptical based on the comparison.
20. A logging tool as defined in any of paragraphs 14-19, further
comprising determining whether the borehole is circular or
elliptical using the borehole formation model.
21. A logging tool as defined in any of paragraphs 14-20, further
comprising performing a vertically one-dimensional ("V1D")
inversion of the borehole corrected MCI measurement signal.
22. A logging tool as defined in any of paragraphs 14-21, wherein
the formation property data is output as one or more of a formation
horizontal resistivity, formation vertical resistivity, dip, or
azimuth.
23. A logging tool as defined in any of paragraphs 14-22, further
comprising performing a radially one-dimensional ("R1D") inversion
of the MCI measurement signal using the circular borehole model;
performing a R1D inversion of the MCI measurement signal using an
elliptical borehole model; and removing borehole effects from the
MCI measurement signal using the R1D inverted measurement signal of
the elliptical borehole model.
24. A logging tool as defined in any of paragraphs 14-23, further
comprising: comparing the R1D inverted MCI measurement signal of
the circular borehole model to the R1D inverted MCI measurement
signal of the elliptical borehole model; and determining whether
the borehole is circular or elliptical based on the comparison.
25. A logging tool as defined in any of paragraphs 14-24, further
comprising performing a vertically one-dimensional ("V1D")
inversion of the borehole corrected MCI measurement signal.
26. A logging tool as defined in any of paragraphs 14-25, wherein
the logging tool forms part of a logging while drilling or wireline
assembly.
27. A logging tool as defined in any of paragraphs 14-26, wherein
the logging tool forms part of a wireline or drilling assembly.
28. A non-transitory computer-readable medium comprising
instructions which, when executed by at least one processor, causes
the processor to perform a method comprising generating a borehole
formation model based upon elliptical borehole characteristics;
acquiring a multi-component induction ("MCI") measurement signal of
a formation using a logging tool extending along a borehole;
processing the MCI measurement signal using the borehole formation
model; and outputting formation property data corresponding to the
processed MCI measurement signal.
29. A computer-readable medium as defined in paragraph 28, wherein
generating the borehole formation model comprises determining the
elliptical borehole characteristics; determining circular borehole
characteristics that are equivalent to the elliptical borehole
characteristics; and utilizing the equivalent circular borehole
characteristics to generate the borehole formation model, thereby
rendering the borehole formation model a circular borehole
model.
30. A computer-readable medium as defined in paragraphs 28 or 29,
wherein processing the MCI measurement signal comprises performing
an inversion of the MCI measurement signal using the borehole
formation model.
31. A computer-readable medium as defined in any of paragraphs
28-30, wherein performing the inversion comprises performing a
radially one-dimensional ("R1D") inversion of the MCI measurement
signal using the circular borehole model; and removing borehole
effects from the MCI measurement signal using the R1D inverted MCI
measurement signal.
32. A computer-readable medium as defined in any of paragraphs
28-31, further comprising performing a zero dimensional ("0D")
inversion of the borehole corrected MCI measurement signal.
33. A computer-readable medium as defined in any of paragraphs
28-32, further comprising comparing the R1D and 0D inverted MCI
measurement signals; and determining whether the borehole is
circular or elliptical based on the comparison.
34. A computer-readable medium as defined in any of paragraphs
28-33, further comprising determining whether the borehole is
circular or elliptical using the borehole formation model.
35. A computer-readable medium as defined in any of paragraphs
28-34, further comprising performing a vertically one-dimensional
("V1D") inversion of the borehole corrected MCI measurement
signal.
36. A computer-readable medium as defined in any of paragraphs
28-35, wherein the formation property data is output as one or more
of a formation horizontal resistivity, formation vertical
resistivity, dip, or azimuth.
37. A computer-readable medium as defined in any of paragraphs
28-36, further comprising performing a radially one-dimensional
("R1D") inversion of the MCI measurement signal using the circular
borehole model; performing a R1D inversion of the MCI measurement
signal using an elliptical borehole model; and removing borehole
effects from the MCI measurement signal using the R1D inverted
measurement signal of the elliptical borehole model.
38. A computer-readable medium as defined in any of paragraphs
28-37, further comprising comparing the R1D inverted MCI
measurement signal of the circular borehole model to the R1D
inverted MCI measurement signal of the elliptical borehole model;
and determining whether the borehole is circular or elliptical
based on the comparison.
39. A computer-readable medium as defined in any of paragraphs
28-38, further comprising performing a vertically one-dimensional
("V1D") inversion of the borehole corrected MCI measurement
signal.
Moreover, the foregoing paragraphs and other methods described
herein may be embodied within a system comprising processing
circuitry to implement any of the methods, or a in a non-transitory
computer-readable medium comprising instructions which, when
executed by at least one processor, causes the processor to perform
any of the methods described herein.
Although various embodiments and methods have been shown and
described, the disclosure is not limited to such embodiments and
methodologies and will be understood to include all modifications
and variations as would be apparent to one skilled in the art.
Therefore, it should be understood that the disclosure is not
intended to be limited to the particular forms disclosed. Rather,
the intention is to cover all modifications, equivalents and
alternatives falling within the spirit and scope of the disclosure
as defined by the appended claims.
* * * * *